As a water pump in related arts, a water pump disclosed in the following Patent Document 1 has been known.
When briefly explaining the water pump, the water pump has a pump housing having therein a pump chamber, a synthetic resin made-drive shaft rotatably supported in the pump chamber, a synthetic resin-made pulley integrally connected to one end portion of the drive shaft through a flange wall, a ball bearing provided on an inner circumferential side of the pulley through a cylindrical metal-made insert and supporting the drive shaft, an impeller provided at the other end portion of the drive shaft so as to be able to rotate integrally with the drive shaft, and a mechanical seal interposed between the impeller and the pulley.
Further, a plurality of penetration holes are provided at regular intervals in a circumferential direction on the flange wall of the pulley. Each penetration hole has the function of inserting a jig for press-fitting an outer ring of the ball bearing onto an inner circumferential surface of the pulley upon assembly of components, and also has the function of draining water, which leaks from the mechanical seal in the pump housing, to the outside.
In addition, the synthetic resin material forming the pulley and the drive shaft contains reinforcing glass fiber material, then strength of the pulley and the drive shaft is increased.